Dodrio can learn drill peck, the best (In my opinion) flying move out there. I'm amazed it can learn fly, so you can keep it with you at all times. Altaria can learn fly as well, but it's weakness is ice. But, you're probably not going to use it to fight ice types. But Dodrio is half normal, and you're probably going to use him to fight fighting, making their moves do regular damage. It comes down to which is your favorite? Personally, I'd choose dodrio, it learns drill peck.

Plus, altaria is Wally's pokemon...it's not nice to steal...